How to assign the drop down value based on the Text value of another column in sharepoint 2010?

I have created a custom list in sharepoint 2010 which contains two columns.

One column is single line of text.

Second column is dropdown which contains 4 values (q1, q2, q3, q4).

• If the text of first column contains as( jan or Feb or Mar) the
  dropdown should automatically select as q1.
• If the text of first column contains as( Apr or may or jun) the
  dropdown should automatically selected as q2.
• If the text of first column contains as( jul or Aug or Sep) the
  dropdown should automatically select as q3.
• If the text of first column contains as( Oct or nov or dec) the
  dropdown should automatically select as q4.

How can I achieve this requirement?